Spark plug



Aug. 25, 1942.

'r. .1. SMULSKI SPARK PLUG Filed July 15, 1940 INVEN TOR THAODORE J SMULS/f/ B) dz 66% Z ATTORNE Patented Aug. 25, 1942 f SPARK PLUG Theodore J. Smulski, Gary, Ind., assignor to Productive Inventions, Inc., a corporation of Indiana Application July 15, 1940, Serial No. 345,474

9 Claims.

scribed in United States Letters Patent No.

2,122,242, granted June 28, 1938, upon the application of Earl E. Bidwell, and which is assigned to the same assignee as the present application.

In spark plugs of the type referred to, the spark gap has been not readily susceptible to adjustment, because a substantial tortional stress caused the taper of the spark gap to become changed whenever adjustment was attempted. Any change in the taper of the spark gap will seriously interfere with the proper operation of the spark plug. In order to avoid the possibility of changing the taper of the gap by attempted adjustment, the commercial plugs of this type frequently were constructed so that the ground electrode extended from the edge of the shell across the shell toward the central electrode along a diameter of the shell and, hence, no adjustment would be attempted by anyone. However, it

would be desirable to provide this type of spark plug with an adjustable ground electrode which would be readily responsive to a bending action and which would be subject to substantially no tortional stress during adjustment of the spark gap. Furthermore, in order to facilitate the manufacture of spark plugs of the type referred to and to reduce the costs of manufacture, it would be desirable if some improved construction of the ground electrode were possible to permit the use of generally one-sized ground electrode for all spark plugs although different initial spark gap distances are required.

It is, therefore, an object of my invention to provide a new and improved spark plug construction which will overcome certain limitations of the arrangements of the prior art and which will be simple and reliable to operate.

Another object of my invention is to provide a new and improved spark plug of the type referred to which will permit the adjustment of the spark gap without changing the taper of the spark gap.

Still another object of my invention is to provide a new and improved spark plug construction of the type of spark plug heretofore mentioned, which will be economical and simple to manufacture.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation, together with further obi jects and advantages thereof, will be better understood by reference to the following description taken in connection with the accompanying drawing, in which Fig. 1 is a cross-sectional View of a portion of the type of spark plug to which my invention has been applied;

Fig. 2 is an end View of the spark plug;

Figs. 3, 4 and 5, are end, front and rightside views, respectively, of the ground electrode; and,

Fig. 6 shows an end View of a modification of my invention, in which a spark plug is provided with two ground electrodes, each mounted in a different manner.

Referring to Fig. 1 of the drawing, I have shown therein the application of my invention to a spark plug having a central electrode l supported by an insulator 2 which may be of the conventional type more commonly in use in automotive spark plugs. The insulator Z is mounted between the upper shell portion 3 and the lower shell portion 4 by means of suitable gaskets 5 and 6. The spark plug shell 4 is provided with interior surfaces 1 which converge toward the outer end of the spark plug shell. An annular or circumferential recess 8 may be provided adjacent the outer end of the spark plug for the purpose of receiving the ground electrode 9 and an end-wall disc I9. The ground electrode 9 and the end-wall disc I!) are retained in position in the annular recess adjacent the outer end of the spark plug shell by turning over a small portion of the metal adjacent the outer end shell 4 as shown at II.

By referring to Figs. 2, 3, 4 and 5, it will become apparent that the ground electrode 9 has an arcuate portion l2 provided with a lug l3, the

purpose of which will subsequently become apparent, and a straight portion I4 which is provided at the end thereof with a sparking terminal l5.

The sparking terminal i5 is at a slight angle to the remainder of the ground electrode so that it extends alongside the central electrode at an angle converging toward the exterior of the spark plug shell as illustrated in Fig. l. The sparking terminal l5 in the preferred embodiment is made relatively short with respect to the cross-sectional area of the straight portion I4 thereby to prevent any action of a tortional stress during adjustment of the spark gap which might change the taper of the spark gap which results from placing the electrode l5 at a slight angle to the remainder of the ground electrode and with respect to the central electrode I. By having and the central electrode I without impairing the taper of the spark gap.

The ground electrode 9 is provided with a lug l3 which cooperates with an indentation in the periphery of an end-wall disc I0, thereby fixing the relative positions of the electrode 9 and the end-wall disc In. The ground electrode 9 and the end-wall disc I are retained in position by any suitable means such as turning over a small portion of the metal adjacent the outer shell 4 as shown at H in Fig. 1, or by any other means of securement. The end-wall disc I0 is provided with an aperture it of such configuration as to permit the extremities of the electrodes 1 and 9 to project to the exterior of the spark plug assembly. While a greater portion of the aperture I6 is generally circular in shape, the portion adjacent to the sparking terminal l of the ground electrode is cut away so as to space the terminal IS a distance sufdcient to permit proper operation of the spark plug.

While the end-wall H] in one form of the invention may be as shown, as comprising a separate disc provided with a suitable aperture, it is to be understood that in certain instances it may be possible to form the end-wall Ii) integrally with the shell 4 by turning over or otherwise working the end metal of the spark plug shell 4 similar to that as at H so that this portion extends a sufficient distance toward the central electrode so as to form a restricted opening. The purpose of this restricted opening is to form a chamber within the shell 4.

It will be readily understood that the relatively thin transverse end-wall portion I!) or the equivalent thereof having a restricted opening of less diameter than the diameter of the interior walls of the shell provides a restricted open chamber. Under normal operating conditions, a charge of combustible mixture is ignited within this chamber, thereby projecting a constricted jet of flame through the opening [5 for igniting the main charge of combustible mixture in the combustion chamber of the engine.

The sparking terminal I5 is arranged at a slight angle alongside the central electrode I, so that the angle converges toward the exterior of the spark plug thereby providing a tapered spark gap within the chamber of the spark plug shell 4 which has a gap at its narrowest point of just proper dimensions closely adjacent the combustion chamber of the engine to provide a suitable spark for idling speeds and to facilitate easy starting of a cold motor.

When the motor is cold, or relatively cool as at idling speeds, the spark will occur across the gap adjacent the exterior of the spark plug, since there is practically no difference in the temperatures and the density of the mixture throughout the chamber of the spark plug. As the motor temperatures increase, however, the mixture within the chamber of the spark plug shell 4 becomes more and more rarefied toward the interior of the chamber, with the result that the spark between the electrodes I and I5 travels toward the interior of the chamber closer to the inner end of the sparking terminal I5. A further and more complete description of the mode of operation of this type of spark plug is to be found in the description of the patent referred to above.

In Fig. 6, I have shown certain modifications of my invention illustrating how a spark plug of the type referred to may be provided with a ground electrode which is adjustable without incurring any change in the taper of the sparking gap during adjustment of the gap. Fig. 6 is a partial end-view of a spark plug having a central electrode la which extends to the exterior of the spark plug through an aperture Mia and an end-wall disc Ilia retained in position with respect to a spark plug shell 4a by a turned over metal portion Ha. The shell portion 4a may be provided at the interior thereof with an undercut portion ll for receiving the curved portion iii of a ground electrode having a straight portion !9 and a sparking terminal 2 9. The straight portion 19 and the sparking terminal 20 of this ground electrode extend across the interior of the spark plug in the. direction of a nondiarnetric chord of a cross-section of the shell 4a in a manner similar to that shown in Figs. 1 and 2. The ground electrode portion 18 may be spotwelded to either the spark plug shell 4a. or the end-wall disc Ilia.

Fig. 6 illustrates how a spark plug of this type may be provided with a pair of ground electrodes and further illustrates another method of mounting the ground electrode- The shell Act may be drilled or otherwise prepared to receive the straight portion 21 of a ground electrode having a sparking terminal. 2'2. The straight portion 2! may be retained in position by riveting, by spot-welding, or by some other method of securement. In each instance, the spark terminals 2H and 22 are at slight angles to the central electrode Ia, so as to provide tapered spark gaps. Any pressure exerted upon these ground electrodes in an attempt to adjust the spark gap will produce a bending action adjacent to the spark plug shell 4a. without producing any detrimental effects due to a tortional stress on the ground electrode.

While I have shown and described my invention in connection with certain specific embodiments, it will, of course, be understood that I do not wish to be limited thereto since it is apparent that the principles herein disclosed are susceptible of other applications, and modifications may be made in the instrumentalities employed and the arrangement thereof without departing from the spirit and scope of my; invention, as set forth in the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States, is:

l. A spark plug having a central electrode tending to the exterior of the shell, the cembination of a shell having interior surfaces converging toward the outer end thereof and bci provided with an annular recess therein cent the outer end thereof, an adjustable g a electrode having a straight portion provided with a sparking terminal, said sparking terminal comprising a surface extending longitudinally e the central electrode to the extremity the. an angle therewith converging toward the ex:- terior of said shell, and a relatively thin endwall for said shell operating. to retain said ground electrode within said annular recess,v said end.-

wall having an aperture for said electrodes thereby to form a chamber within said shell.

2. In a spark plug having a central electrode extending to the exterior of the shell, the combination of a shell provided with an annular recess therein adjacent the outer end thereof, an adjustable ground electrode formed with an arcuate portion adapted to seat in said annular recess and having a straight portion extending to the proximity of said central electrode and terminating with a sparking terminal, said sparking terminal having a surface extending in a lateral direction along the central electrode to the extremity thereof at an angle converging toward the exterior of said shell, and an end-wall disc having an aperture for said electrodes, said ground electrode and said disc being seated in the annular recess of said shell, said end-wall disc cooperating with said shell to form a chamber therein.

3. In a spark plug having a central electrode extending to the exterior of the shell, the combination of a shell having an annular recess therein adjacent the outer end thereof, and an adjustable ground electrode having a. straight portion terminating with a sparking terminal, said sparking terminal having a surface extending longitudinally along the central electrode to the extremity thereof at an angle therewith converging toward the exterior of said shell, and a relatively thin end-wall operating to retain said ground electrode in the annular recess of said shell, said end-wall having an aperture for said electrodes thereby to form a chamber within said shell.

4. In a spark plug having a central electrode extending to the exterior of the shell, the combination of a shell having an annular recess therein adjacent the outer end thereof, an adjustable ground electrode having a straight portion terminating with a sparking terminal, said sparking terminal having a surface extending longitudinally along the central electrode to the extremity thereof at an angle therewith converging toward the exterior of said shell, and an end-wall disc having an aperture for said electrodes, said ground electrode and said disc being interlockingly retained in the annular recess of said shell, said end-wall disc cooperating with said shell to form a chamber therein.

5. In a spark plug having a central electrode extending to the exterior of the shell, the combination of a shell provided with an adjustable ground electrode mounted within said shell and having a straight portion extending to the proximity of said central electrode, said ground electrode having a sparking terminal at the free end thereof comprising an enlarged member having a surface extending alongside the central electrode to the extremity thereof at an angle converging toward the exterior of said shell, and a relatively thin end-wall for said shell having an aperture for said electrodes, said end-wall forming a chamber within said shell.

6. In a spark plug having a. central electrode, the combination of a shell provided with a circumferential recess therein adjacent the outer end thereof, an adjustable ground electrode formed with an arcuate portion and a straight portion having a sparking terminal at one end thereof, said sparking terminal comprising a member having a surface extending alongside the central electrode at an angle thereto converging toward the exterior of said shell, and a disc having an aperture for said electrodes, said ground electrode and said disc being seated in the circumferential recess of said shell, said disc forming a chamber within said shell.

'7. In a spark plug having a central electrode, the combination of a shell provided with an annular recess therein adjacent the outer end thereof, a ground electrode formed in arcuate shape and having a sparking terminal at one end thereof, said sparking terminal extending alongside the central electrode at an angle converging toward the exterior of said shell, and an end-wall having an aperture for said electrodes and operating to form a chamber within said shell, said ground electrode being retained in the annular recess of said shell by said endwall.

8. In a spark plug, the combination of a central electrode, a shell therefor having an apertured end-wall forming a chamber therein, said chamber having a circular cross-section, a ground electrode mounted on said shell within said chamber and extending in the direction of a non-diametric chord of said cross-section to the proximity of said central electrode thereby to permit a bending adjustment thereof adjacent said shell without substantial tortional stress, and a sparking terminal formed at the free end of said ground electrode, said terminal extending longitudinally along the central electrode at an angle thereto converging toward the exterior of said shell.

9. In a spark plug, the combination of a central electrode, a shell therefor having an apertured end-wall forming a chamber therein, said chamber having a circular cross-section, a ground electrode mounted on said shell and extending in the direction of a non-diametric chord of said cross-section to the proximity of said central electrode thereby to permit a bending adjustment thereof adjacent said shell, and a sparking terminal at the free end of said ground electrode formed so as to be relatively short with respect to the cross-sectional area of the remainder of the electrode, said terminal relative to said central electrode being at an angle thereto converging toward the end-wall of said shell Y and extending to the exterior of said chamber.

THEODORE J. SMULSKI. 

